selenium

@Nimitz
Sorry for slow response, lots of hectic here currently.
Battery replacement is still in limbo but I've finally managed to get a return/refund organised for the blasted gels. Just waiting to complete that.
Esener is currently front-runner because price and also local company. They offer a very good price if you're willing to take 3 units, otherwise you need to go through a reseller.
Only caveat: the Esener battery doesn't seem to have a way to talk to inverters (via CAN/RS435/whatever), but I bought a Victron SmartShunt recently, so I don't really care about that.
The battery will deal with max. discharge protection itself and the SmartShunt can tell me where the battery state is at, and also remotely.
I have an RCT 2kW (genuine Voltronic), and aside from it's inability to deal with lead gel batteries, it's a nice little unit. I imagine the 3kW variant will do equally well.
FYI: both your inverter options seem to be Voltronic units, but be aware that Voltronic clones also exist.
@Coulomb did an EXCELLENT write-up about how to tell real from clone - do a forum search, you find it.
So to recap: I've pretty much decided on Esener, but don't have any experience yet, so will only be able to report back in a few months.

@Nimitz
Sorry for slow response, lots of hectic here currently.
Battery replacement is still in limbo but I've finally managed to get a return/refund organised for the blasted gels. Just waiting to complete that.
Esener is currently front-runner because price and also local company. They offer a very good price if you're willing to take 3 units, otherwise you need to go through a reseller.
Only caveat: the Esener battery doesn't seem to have a way to talk to inverters (via CAN/RS435/whatever), but I bought a Victron SmartShunt recently, so I don't really care about that.
The battery will deal with max. discharge protection itself and the SmartShunt can tell me where the battery state is at, and also remotely.
I have an RCT 2kW (genuine Voltronic), and aside from it's inability to deal with lead gel batteries, it's a nice little unit. I imagine the 3kW variant will do equally well.
FYI: both your inverter options seem to be Voltronic units, but be aware that Voltronic clones also exist.
@Coulomb did an EXCELLENT write-up about how to tell real from clone - do a forum search, you find it.
So to recap: I've pretty much decided on Esener, but don't have any experience yet, so will only be able to report back in a few months.

Thanks @Coulomb, so, I guess the premature float bug is not at issue here, since @selenium does not have solar panels as far as I understood it, its just too many cycles on the batteries that are not designed for this kind of use, really... we've been having 2 to 3 load shats per day in recent times, now 1 or 2 per day, if it happens during sunshine and you have solar panels, no worries, but hey, yesterday at noon to just after 2PM and again at 10PM until just after midnight... during the day when the fscking clouds aren't there, no worries, but at night, certainly the battery has to make do... but.... again the OP has no panels, as far as I know...
So, @selenium, I suspect your batteries, however cheap you got them, are seriously the worse for wear and you can try and baby them back to slightly better health, but the outlook is somewhat on the grim end of the scale, I'd say...

OP has the perfect recipe for batricide: 24V system (so high battery current for a given load, and no patched firmware), lead acid battery, and frequent load shedding. Default settings are not designed with frequent load shedding in mind.
The biggest problem is the low DC cut-off setting. This is usually around 10.5V per 12V module, which is appropriate for maximum run time in the assumed RARE condition that it's needed. When you have load shedding multiple times per week, this is way too much discharging for lead acid, and they quickly lose capacity and increase internal resistance.
With frequent load shedding, it's imperative to set the low DC cut-off (when using a lead acid battery) to 12 V per nominally 12 V module, i.e. 24.0V in this case, or 48.0V for 48V inverters.
ALL Voltronic inverters come with the premature float bugs from the factory. They just don't believe it's real. It means that when charging from solar, when about 75% charged and a cloud comes by, the inverter sees low current into the battery, and decides incorrectly that this must be because the battery is full. It only wants the battery to be within half a volt (quarter volt for 24 V systems) of the FLOAT voltage to declare it full. Of course, it should be nearly the BULK/ABSORB voltage and low battery current to declare it full. If charging mostly from solar, which is what most of us like to do because it's free once the system is paid for, this bug causes the battery to be chronically under-charged. Lead acid suffers from this, accelerating the degradation that is already bad because of the excessive discharge.
As to what can be done: charge each battery module separately with a car battery charger. Watch the battery voltage. If it shoots up immediately to say 14V, that's not a good thing; it means that the battery acid is almost water. If you're lucky, the battery module will recover a little, and the battery terminal voltage will actually go DOWN as it is charging; this is a good sign that the internal resistance is falling.
As for how long to set the equalisation charge to work around the premature float bug, it's a delicate compromise. Too long and you could over-charge the battery and boil out the small quantity of water that is in them. Too short and you're not charging it enough. 60 minutes seems like a good place to start. Sadly, you'll have to watch the battery very closely. Worse, the chances of recovering your existing battery are very slim. That's one of the reasons that lithium batteries are so popular: they're not so delicate, and also they have a battery management system protecting them. Plus, lithium chemistries don't mind frequent discharges, as long as it doesn't go below about 5-10% SoC very often. Of course, they cost a lot more up front. Also the options for 24V systems seem to be quite limited.

FYI, there is a premature float bug on some of the Axperts which causes it to never reach the bulk charge voltage, it just charges to the float voltage and stays there so the batteries never fully charge. Just make sure your inverter is actually reaching the bulk voltage. You can overcome this by using the equalization settings to run daily at the same voltage as your bulk setting.

So THAT's what that table is for - thank you! Bloody hell. I will update the cut-off voltage and report back but it really helps to now know what that table is for and how to use it. Thanks again!
I will also check the voltage at the inverter vs. the batteries to get a feeling for what impact the cables might have.
As an aside: You have my complete agreement on the lead money wasting items - like I said, I got them very very cheap. The idea is to sell them once I have a better grip on the systems and terminology, and then move to LiFePO4.
But you have to learn somehow, and this is a good, not too expensive school, with lots of very knowledgeable people willing to share their experience and know-how.

Thank you - every day a little more knowledge 😀

So THAT's what that table is for - thank you! Bloody hell. I will update the cut-off voltage and report back but it really helps to now know what that table is for and how to use it. Thanks again!
I will also check the voltage at the inverter vs. the batteries to get a feeling for what impact the cables might have.
As an aside: You have my complete agreement on the lead money wasting items - like I said, I got them very very cheap. The idea is to sell them once I have a better grip on the systems and terminology, and then move to LiFePO4.
But you have to learn somehow, and this is a good, not too expensive school, with lots of very knowledgeable people willing to share their experience and know-how.

Well, I don't like these lead money wasting items, but if you look at your manual, assuming you discharge at .2C or below, then the Battery cut off should be 1.75V * 6 (cells per battery) * 2 (batteries in series) = 21V
There's a difference tension wise between a cell with 0 load and a cell with a load and your cables also come into play, depending on the cable dimensions and the connector quality and crimp quality between the cable(s) and the lugs/connectors you could have some extra resistance and thus Voltage drop, once current starts flowing...

Oh how I remember cursing them 🤣

I would also bring that cut-off voltage down by at least another 1V, maybe even 1.5V at the same time I would definitely decrease the charging amps to 15 amps to reduce the wear on the cells. These batteries prefer nice slow steady charging to keep them healthy.