Great post with lots of detail! I have had MyQ for years and hated it pretty much at first use. Back then, they were asking for a monthly fee for the "privilege" of integrating it with Google.
Since the MyQ integration for HA is now dead, I have ordered a Ratgdo and am patiently waiting for it to arrive. I tried the Anthom.tech opener, but that does not work with most Chamberlain/Lift master opener made after 2011.
The primary reason to virtualize is to maximize the "bang for your buck" on your hardware. Containers are great, but have their limits.
So long as you have a desire to learn it (and the budget), I say dive in with Proxmox and see how you can put that hardware to use. VMWare ESXi is more common in a business/enterprise setting, but costs money to for anything beyond the basic functionality after the evaluation period.
I second Paperless NGX. I have been using it for a few years, and it has been working great!