I have various Mikrotiks that I arbitrarily set up for this sort of thing. Handy thing with them is that you can script the startup mode, like if it can ping 8.8.8.8 on ether1 then set it up as a router, if there is no internet on the WAN port then switch to bridge mode or some such. I’ve got a couple of different scripts to save having to manually reconfigure it every time.

$30-50 is the cheapest you can get a data service over there? I have multiple unlimited 5G SIMs for £16-18 per month with unlimited data.

You can work this out yourself pretty easily. How much does your electric cost? How much does it cost to run that 80W Pavilion? It’ll be pennies per day. Unlikely that it would make financial sense to upgrade, which is why I still have noisy HP G7s in my rack, cheaper to keep them than upgrade.

Mines round my mums house as I have no fixed internet at mine. House is up for sale so it has to be explained to potential buyers that it isn’t part of the house and it’s not usually this warm or noisy in here when they get to the room with the rack in!

I’ve heard of PDUs definitely in passing but I didn’t know that they could have some leakage current

They don’t. Maybe the equipment connected to them will but the PDU leaks nothing of any significance, it’s fairly passive.

No.

Whilst the drives might be fine there’s not much point trying to cram enterprise drives in a desktop PC. Waste of time this, better off just throwing any old drives in and making sure your backups are in place instead.

If you want to use enterprise gear start with the motherboard and memory, you’re doing this backwards (I’ll refrain from doing the upside down joke here!)

Whilst I am with the “yeah, that’s irrational” crowd, there are these things that might help allay some fears. https://www.controlfiresystems.com/products/fire-suppression/ceasefire-pre-engineered/

Anecdotally out of the maybe 100 drives I have dotted around here the failed ones are mainly Seagate.

In the field though, makes no odds. Most of the kit I am supplied with comes with Seagate, not had any issues with them.

What doesn’t work? Doesn’t look like it needs “improving” specifically.