I coded some games via Pygame so I could play and test them on my L5 but realized, that it wouldn’t run that smooth as it would on a PC. I also used the img = pygame.image.load("<imagename.extension>").convert() for all images, so it wouldn’t load the images for every frame.
Is there a way to make the GPU rendering pipeline more reliable?
A different LANG?
Would you mind to share some pics of your games? I want to know what kind of games and effects make problems to L5 GPU (even if problems are code related).
Just a side note: In future (when I get L5) I want to test Unreal Engine 5 (the engine I am working with). Not sure if it can even run on L5, but what stops me to test it and share experience here? 
If it runs, performance for 3D environments could be better compared to other engines (because of “Nanite” - new render pipeline).
sure!
I co-developed this game. I’m not VantaTree. V1_2 includes the GUI for making it fully usable on the Phone when Resolution is set to 100%. The ‘slide’ effect in Main Menu are giving me framedrops. Except for that, It runs fine.
As for the games I developed, I realized that having more than 1 Sprite in use ingame would slow down the performance on L5 heavily. L5 really has its limitations with enabling effects.
I want to test Unreal Engine 5 (the engine I am working with). Not sure if it can even run on L5
I doubt that, sorry.
Sounds to me like coding related loading issues while loading these pictures. Can you maybe preload these 7 pics? I have no idea about Pygame engine, but you said rest of the game (even with higher detailed background images) runs smooth. So there should be also a way to fix this issue.
Seems to me strong enough: Gaming on L5
And UE can be build very light by disabling many features. But I expect nothing, just want to experiment with.
The images will only load once they appear on-screen 
just what it needs to kill any sprite etc. off-screen.
Seems to me strong enough: Gaming on L5
maybe I’m extremely spoiled but even in some clips featured in the link you shared, I can see low fps in SuperTuxKart (for hockey mode you want 50fps at least to give the winning rate as much chance as possible).
UE can be build very light by disabling many features.
goes with
L5 really has its limitations with enabling effects.
I mean… surely a custom-made engine (in Allegro, SDL, etc.) would run more efficiently, right? The tradeoff being, it requires a greater investment of development time, a lack of features, etc.
I have made my own basic game engines tailored to the game I was making, but that’s about where my experience ends. 
Sorry if that doesn’t help much…
I know right. Just saying that (low-poly) 3D games are possible. And I have more experience in optimizing such stuff then optimizing “board-games” like yours. So sorry if my answer was not helpful in any way.
Depends on …
If you are looking for “most efficient engine” then you have decide from game to game different. A specific game engine for a specific game has a pro: it is as light as it needs to be for that game without unused features. On the other hand you are maybe not able to optimize this engine to the best of the art.
And game performance is also not only made by engine, but also very much by artists and game code writer. You can do exactly same stuff in many different ways - even as simple as display pictures like wednesday does in his game. Sometimes optimization just means a tradeoff like “more GPU usage here, but less CPU usage there” which also can result in higher frames.