You can try seeing if you can set the speed/duplex of NIC/ports manually if auto-detection keeps getting it wrong.

Unifi I like the APs for mesh & multiple SSID+vlans but I keep them on dedicated vlan with zero internet access because I don’t trust that I properly followed instructions to disable opted in analytics/telemetry. The mgmt software is alright but new UI wastes a lot of space. The PoE switch was alright until it stopped being able to keep a config last year. USG router I kept less than a year because it was too slow with any useful features enabled. I’ve glanced around at replacement APs here & there but pretty much waiting until I have more wifi 7 compatible devices and that’ll be another couple years.

Self-host your own ACME server. Then you can use certbot pointed there.

These instructions are old so not sure if newer/better ways, https://blog.sean-wright.com/self-host-acme-server/

This project, https://neko.m1k1o.net/#/getting-started/examples , looks like a good base to try running regular GUI apps via docker & web.

edit: and here’s the git with Dockerfiles, https://github.com/m1k1o/neko-apps