I'm not sure I fully grasp what you want, but Restic is excellent. I use a cronjob to back up on a schedule. It's command line only. I think there's a tool to make it a GUI but I haven't tried it. They have a Docker image available but it's weird, you have to pass commands to it, it runs, then shuts down when it's done. I love Docker but that didn't quite work for me.

I use Backblaze B2 for storage, but any S3 will do. Restic supports all sorts of storage targets.

Credentials and things go in an .env file, or you can put everything into the command line every time.

When it's time to restore things, you can fricken mount the whole backup you want and browse the files, copy and paste what you need, etc. That part is really cool to me.

Backblaze is $5 or $6 USD per TB per month, so 500GB will be about $36USD a year.

I really like duplicacy. It's just a single executable you add to your path, then configure it to back up to basically any remote you want. I don't even bother to run it in a container since it doesn't have dependencies. Encrypted, compressed, deduplicated, incremental backups. The algorithm is pretty slick too. It can back up multiple machines to the same repository, and it'll dedupe across them without any locks required.

Duplicacy CLI is free, and there's a front-end for a reasonable fee. I think $50 for the first year, then $10 for every subsequent year.

For storage, you can just go with whatever is cheapest/easiest. I use a gdrive I'm paying for regardless for effectively free storage. But if I didn't have that, Hetzner seems very appealing. I think it's $4/mo for 1TB? Very reasonable, and you wouldn't need to worry about api calls or chunk size / file count like you would with S3/B2/StorJ.

If you have already borg, why don't use it?

I use Veeam.
The Agent is free amd can do integrity checks
The B&R server can manage multiple systems has a steeper learning curve can be free (with a reduced featureset) or operated with a license.

I use Veeam at home and at work and I quite love it.
(And they recently started supporting Proxmox)

For me borg is ideal. Once a month I run a backup.

I use Hetzner Storage Box for my backup needs - TrueNAS handles this for me on a regular interval and encrypts them before upload (yay rclone!). I needed a bit more storage than you, to the tune of 5TB, and for this much data they were the cheapest (12eur / 15usd per month iirc).

Consider slightly more storage if you need snapshots. For my storage box i enabled them, and now have a history of last 4 monthly backups.

If you use rclone, you can mount the remote backup as a fuse filesystem and browse your backup like it would be a local file - extract what you need only. Any livecd / USB with rclone can help you rescue your data in case of disaster.

I use Kopia to perform incremental encrypted backups (with some retention policy of up to two years) and store them on Backblaze B2, which is reasonably cheap.

I haven't changed much in years, still run a truenas box (was freenas before) with 5 spinning rust drives and never lost any data yet (bang goes something now I've said it). Currently duplicati but some stuff is just backed up manually still. Each to their own like, and immich on truenas for backing up photos and videos

Perhaps urbackup? She might not be the most pretty girl but works like s charm. It works on window, Linux and I do believe Mac as well.