Is the Electrum seed compatible with other wallets?
There are different "backup-standards".

Some use BIP39 (mnemonic) which lacks a flexible wordlist and versioning. It's used by Ledger, Trezor, Bitpay/Copay, etc.

Electrum uses a different – more flexible – mnemonic backup concept which is incompatible with BIP39.

There is also the BIP32 keypath which can be different among wallets. Example: you can restore a Trezor BIP39 mnemonic in iOS BreadWallet, but due to missing support of BIP44 in BreadWallet, the funds cannot be recovered there.

If you switch away from a wallet, consider sending all your funds to the new wallet (although this has some privacy implications, it's generally good for security due to the re-keying).

But as long as you keep your backup (seed / mnemonic), there will always be a (theoretical) option to recover your funds. If the wallet didn't stick to a standard and died (no maintenance, etc.), then you may need to contact an expert for a manual recovery.

If you use a mnemonic, make sure you use at least 24 words.