can I use ethernet cable instead of wifi for migration assistant

Yes. However the procedure is slightly different if you are directly connecting the Macs to each other vs. both Macs being on a network. Which do you want to do?

Do both of your Macs have an RJ-45 ethernet port? Some of the new Macs no longer have an ethernet port and require an adapter. Actually, it will be most helpful to know the exact model of each Mac and the version of macOS on each.

As small addition to what Martin said: I suppose you do have a Time Machine backup of the old mac, right?

It is probably simpler, and faster, to migrate using that TM drive attached directly to the new mac, and therefore bypassing any network issues.

If the new computer is going to be the Apple Silicon M1 Equipped Computer - would suggest Only Migrating the User Account and nothing more.

1 - Apple Silicon with either Big Sur macOS 11 or Monterey macOS 12 Only Support everything 64 bit and there is no workaround.

2 - Issues that may exist on the older computer will be migrated to the New Computer. This would badly pollute the new Original and Pristine installation of the new OS.

3 -  Applications, extensions and Software Drivers may or may not even work on the new computer.

4 - IMHO - it would be best to only install new application etc Directly from the Developer or the Apple Apps Store.

5 - Due Diligence on New Applications and make sure they are Monterey / Big Sur compatible and factor in the ARMs CPU of the Apple Silicon Computer