I am really sorry for what you are going through. When I set my P1S upthe LAN Only option didn’t appear untill the printer was at least connecting to my wi-fi. At first it was only getting a 0.0.0.0 address but it was showing the wi-fi name at which point I was then able to put an IP reservation for it’s MAC on my router.
Other things I can think of, some of these are repeats buts it’s just me trying to remember everything.
Printer will only connect to the 2.4gHz On my router I gave the 2.4 and 5 gHz bands different names. (My PC is on the 5 gHz side).
Look to see if IPv4 & IPv6 are both enabled. Maybe try running IPv4 only and if you get a connection then re-enable IPv6.
The formatting of the SD card is pretty specific and I know I’m not the only one that had issues getting it right. But part of the issue is that there is just no feedback from the printer if something is not right. Use a 32 GB card (or smaller). format to FAT32. You can try formatting on the printer but you may end up needing to use a PC. Make sure upper/lower case match on SSID and PW.
Question: does your printer show Logged in or Not Logged In at the ACCOUNT prompt on the printer display (this is not the wi-fi login).
There are several threads here and on Reddit. No one-size-fits-all solutions.
Sounds like you would love to get back to being able to use Handy but at least if you can get LAN only to work for now you can at least use the printer.