If there is docker image for what you need, use docker image.

If not I would recommend systemd-nspawn, it’s chroot but can run systemd init, with efforts you can run GUI applications from it too., wiping that is just sudo rm -rf.

I wish there is everything for Linux.

fsearch has the looks but last time I tried I needs to wait for it to scan, no background indexing.

Also using PurelyMail, tt’s the cheapest non-free email service I can find.

It passes email delivery tests, setup SPF, DKIM and DMARC easily without issue.

The downside is that it’s basically one man handling whole this service, but I assume this service has been fully automated because the margin of profit is so low.

I do this in winter, warms my room a little while doing (what I think is) good.

On Ubuntu 22.04 based distro, you can try install HWE (hardware enablement) kernels but you need a phone that can share WIFI/mobile connection through USB cable.

sudo apt update; sudo apt install linux-generic-hwe-22.04

Try posting output of lspci command here, gives us more information about your laptop hardware.

some sort of dashboard with monitoring and statuses of all my services

See if Uptime Kuma suits your needs.

Are there any major no-no things a newbie might do with Docker/selfhosting that I should avoid?

Allow password based SSH authentication, you should look into key based authentication

I wanted to have it behind a domain, how would I achieve it?

Use a reverse proxy (like caddy) which serves different content based on domain name.