This isn’t really an answer to your question, but you should honestly try Netrunner. It’s a cool game that previously was originally created by Richard Garfield, briefly lived at WotC and then was rebooted and run by Fantasy Flight Games as Android: Netrunner, but now is 100% community managed.

https://nullsignal.games/ is the community managing the game, they release new expansions about once a year and run tournaments. You can print and play the game 100% for free and there is no artificial scarcity. The community is small but active. A new expansion just came out in early March, Vantage Point. They also maintain a set of “starter decks” for newbies.

You can also play online for free at https://jinteki.net/ - people there are very welcoming and many are very happy to teach new players.

I enjoy Magic the Gathering, but I hate that it’s leashed with copyright and patent stuff, and basically pay to win with Wizard’s bogus artificial scarcity.

Not exactly what you're asking for, but Magarena is an open-source Magic: The Gathering clone.

https://magarena.github.io/

No artificial scarcity there.

Lauren Bobert is pretty close

Assuming you're talking about original art I think Etsy is your best bet. Sometimes eBay has some. You also get some really cool altered art where they extend the background etc. Its not cost effective though and there's a lot of ai art now. My rule of thumb is anything over 4$ gets proxied now for a deck. There are sites like https://tolarianlibrary.com/ that do pretty good 1:1 copies that pass the sniff test for casual play. I really really hate when art is economically locked, philosophically art should be for all. I try and always proxy the prettiest version of cards. The secret lair copies aren't perfect but their pretty darn close. There's a handful of other sites I can DM you that I trust. To answer your original question I think there is a site for proxy designs, but they don't give you the cards just the designs.

It's no less commercialized, and it's not physical, but I've been playing Hearthstone for mostly free for over ten years. Plays like MTG, but faster, and implements a lot of randomization that's near impossible to do with physical cards.

So this is something I'm kind of versed in. For starters, there are a ton of places to get cards printed with the same look and feel of mtg. printingproxies.com was my go to when I still actively played. They let you do custom cards and also let you do altered backs which I use to make double face tokens.

If you're looking to get into tourney on them, there's a few Chinese counterfitters that operate out r/bootlegmtg last I checked. They have some pretty advanced techniques and can even clone the little foil badges. Last I looked, the only genuine tell is that they have black core instead of blue so they're darker if you shine a light through them.

As far as the fun, I actually used to run a custom commanders game in my local circle that was very popular. You make your own commander and your other players vet them. This has turned into a combination mtg/RPG where we have character sheets that define what card can be our commander in the card game and then the spells in the deck are our spells in the RPG.

I thought this was about Marjorie Taylor Greene for a second.

Hell's Cube (It works.)

It's been a minute since I last tried it, but: Forge: The Magic: The Gathering Rules Engine https://card-forge.github.io/forge/ & https://github.com/Card-Forge/forge

It's essentially MTG: Shandalar - but free & opensource. So basically you start with some starter deck, roam the lands to defeat color-coded wizards and dungeons for ante-cards and money (which you use to just buy cards from vendors), build deck, and ultimately defeat the elemental gods etc. Shandalar. :)

The game has actual MTG cards (can be downloaded via the game's menus).

I've seen using mpcfill.com to make your list of desired cards, and then using the built in export over to makeplayingcards.com.

About proxy legality, outside of sanctioned events even Wizards is cool with proxies (they refer to them as playtest cards, not to be confused with actual playtest cards created during development) existing, so long as they are different enough from real cards they can't be considered fakes (typically done with either a different backing or adding some text to the bottom) and retailers don't make products for sale using the copyright symbols (colors, tap/untap) without permission.