I did make an attempt to switch from GnuCash to Firefly III, but had to switch back. As loathed as the GnuCash GUI is, Firefly III simply did not come close to the speed with which I could enter transactions in bulk via the keyboard. Plus, I was too used to GnuCash's data model and way of doing things.

The reason I was drawn to FF III in the first place was because of its aesthetic appeal and visualization features. The graphing and reporting abilities of GnuCash are not to my taste.

After some time, I settled down to converting from Gnucash to Ledger using PieCash (https://github.com/sdementen/piecash), and visualizing the ledger file using LedgerWeb (https://vifon.github.io/ledger-web/). A bit of a workaround, but can be scripted and works fine for me.