MysterD: If we want to go there - sure, to get an account & pay for these games just to get these files in the first place to archive (so I can back them up on DVD, CD, BR, flash drive, another HDD, whatever) - I need a GOG account; need to buy the game;
go onto web browser or Galaxy app; sign into my online GOG account and download the files from web browser or Galaxy app. toxicTom: On GOG I can choose which browser (within limits... or else the site is broken), I can use LGogDownloader or gogrepo.py. I can even make my own downloader client with a bit of programming effort. I don't have to trust Galaxy.
Is there a way to get games downloaded from Steam without installing the official client?
Unfortunately, there is not. Nope.
You will need Steam game-client application to grab yours games for the first time, at least.
You can always back-up games folders (it's digital, they're your files) - but from there, it's up to you to do the homework, looks around online, test yourself, or whatever...to find out if a game over there has DRM. Thank God for wiki's, GOG threads, and whatnot on that stuff.
One of the differences b/t GOG and Steam - Galaxy's client is optional (you can still grab your games via a web browser), meanwhile the Steam client is required.
Epic Store works the same way as Steam, also - you need the client to get your games from there. From there, going to have to do the homework online or test it out yourself to find out what over there has what DRM.
Regardless, either way - Steam or GOG - you still have to sign into an account, buy the games, and download them online. All on you to back them up yourself.
EDIT:
I wish Epic, Origin, and Steam were often a bit more open if games have DRM or not. Especially on the "no DRM" part, as often that's not listed and not made public.
I do love that with GOG, you pretty much know that your Single-Player portions/campaigns are going to likely not have DRM-related issues, since games are DRM-FREE over there.