Earlier quoted context omitted.
Buy an external hard drive or SSD, download the photos to it, put it in a safe place away from your other computer stuff.
That's viable for sure, but one thing I'd like is regular backups of the photos from my phone (where most I take most of my photos). That's the nice thing about Google Photos with Google One - all my stuff is backed up to the cloud regularly. I understand, though, that this comes with some risk.
- I recommend Syncthing (easy) or Seafile (more features).
Both are free for personal use but the latter is a product (paid plans, support), Syncthing is more of a 'project' (both work great).
You can self-host the recipient machine at home or on some cloud (depends on your internet connection, needs, skills, and budget, I guess).
[IMHO it's a must-have skill in our historical era to be able to manage data at a basic level, just like managing one's finances, or health status; so I recommend learning 'enough' about it.]
- "Data that only exists once (1 original copy) does not exist." — the idea of a single point of failure without possible recovery.
Have at least 3 copies: 1 original (e.g. phone, laptop); 1 'repository' (file server) which aggregates all sources and becomes your central source of authority; 1 backup. (this ensure that you never go below 2 copies, if any 1 fails). I use Google Photos too in addition to Syncthing — sort of a failsafe for uploading.
- For long-term storage (photos usually qualify), consider bit rot — the fact that storage devices simply fail partially randomly, i.e. you lose literal bits here and there from time to time, unless precautions are taken (e.g. self-healing ZFS array).
This makes cloud services usually attractive, they take care of all the low-level behind-the-scenes shenanigans. Conversely, long-term physical backups (HDD) should periodically be either fully checked or rewritten — but they're far cheaper, now below $25/TB, so it's easy to just have two backups, one 'hot' (disk online) and 1 'cold' (disk in a dry closet). I would recommend a filesystem with checksums.
If you need more advice or guidance, feel free to ask questions.