I too will say something like this. For bitcoin, Guarda wallet only support the legacy type of bitcoin address. Nothing like nested segwit, native segwit and pay-to-taproot. Atomic wallet at that time and as of now, it is only supporting legacy address too. It is good for developers to be active and do what are the latest.
I can list many coins that Guarda is not also supporting. If there is any doubt, you can ask me to list the coins. And they are common coins.
In this case, I used Electrum for Bitcoin and Metamask for Altcoin. Both wallets were installed and not so much space.
Undoubtedly, if Metamask is open source, it is one of the best altcoin wallets. But not supporting many other coins too. It does not support the coins that have their own blockchain without been a token. Although Metamask can support their pegged versions.
AFAIK trust Wallet is not completely open source whereas Mycelium is however this is not safe for storing cryptos for long period as I said earlier cause it is prone to attacks also user feedback of mycelium android is not great cause it is filled with a lot of glitches and even many people claimed that they can't see their balance even after enough confirmations.
I even know Mycelium to support bitcoin, ether and ERC20 tokens. I have not seen it supporting others like TRC20, BEP2, BEP20, solana, arbitrium, optimism, polygon and their tokens and others.
I do not know why there is no diligence in developing an open source multi-currency wallet, but even those that claim to be open source will be far from closed source wallets and will not get the same features.
As mentioned above, Unstoppable wallet is one. But not having some coins as of now and can not be used for staking. There is no desktop version for now too.