While using Monero GUI wallet, I have been suggested to try Feather wallet instead. So this is what worked to reuse my existing Monero GUI wallet inside Feather app without loosing data and without need of a long synchronization.

I have tried to set I2P port (used by other I2P client app):

- Qt: 6.7.0
SSL: OpenSSL 3.2.1 30 Jan 2024
SSL build: OpenSSL 3.2.1 30 Jan 2024
Tor version: 0.4.8.10
... D] (:0) wallet .keys search initiated
... D] (:0) "wallet .keys search completed in 2 ms"
... W] (:0) failed to create compose table
... W] (:0) Proxy:  "127.0.0.1"   1234
... D] (:0) WebSocket connect: "ws://longstringhere.b32.i2p/ws"
... D] (:0) WebSocket disconnected

after using default port suggested in the app (inside i2pd.conf described as "SOCKS proxy"), it started working:

... D] (:0) WebSocket connect: "ws://longstringhere.b32.i2p/ws"
... D] (:0) WebSocket connected

then there were options (among other) to:

Open wallet file
Restore wallet from keys

I have selected first one as it suggest no loss of data. Yes, it displayed that it found a wallet, which location is ~/Monero/wallets/Wallet/Wallet.keys I have selected "Open on startup" tickbox and "Open wallet".

Result:

Unable to open wallet
internal error: "/home/me/Monero/wallets/Wallet/Wallet.keys" is opened by another wallet program

After closing Monero GUI and returning to Feather wallet, I could repeat "Open wallet file" step.

It opened the wallet, showing right balance and immediately ended up "Synchronized".

Under "View" menu i can show tabs: Exchange, Coins, Mining. That seems to be more useful than Monero GUI. The homepage shows a crowdfunding campaigns and news. I like that i can use my existing I2P connection, not only Tor.