Aperture replacement in late 2021: Keep photo edits AND Keywords?

What exactly do you mean by "preserve edits"? If you mean preserve them in a form that allows you to re-edit the shot from the same point, then almost no apps will do that. The one that tries - CaptureOne - says:

Every photo editing software package has its own algorithms when it comes to adjustments – these are usually not transferrable between programs. Capture One Pro will import many global adjustments and do a best-effort at converting them to their corresponding Capture One Adjustments. You will have to review these converted adjustments and refine all of your images after importing into Capture One

So the best you'll get is a "best guess", and this applies only to global edits, not to any brushed effects. In my experimenting I found that very few actually made it across and didn't need refining.

For most, what happens is you export the Master and an edited version and then add those to the Library on the new app. Or, starting from scratch, you re-edit the images in the new app.

All of them import keywords - the specifics will depend on which app you choose.

Viable alternatives to Aperture include:

Lightroom Classic

CaptureOne

OnOne Photo Raw

Exposure

Forget Luminar for a couple of reasons. Aperture was a DAM, a Digital Asset Manager. Luminar's support for managing your photos is, frankly, rudimentary at best. You'll need an app that's a lot more capable in the area. Further, the business practices of that company leave a lot to be desired. They have a very nasty habit of developing an an app, then abandoning it, and starting a new app, and with no migration path from the old one to the new one, leaving the user in the position of starting over from scratch. They've done that about 4 times now. Buying their product is asking to be mugged.

Photos for Mac will preserve the Aperture edits and the keywords, when you open an Aperture Library in Photos. Only, it cannot recreate Aperture's hierarchical keywords. Instead of one hierarchical keyword (category, sub category, sub subcategory, ...) you will get separate keywords for the category, subcategory etc.

The edited versions will be migrated using the previews created by Aperture, so you will have to ensure, that Aperture renders full resolution, high quality previews, before you migrate the library. We can view and share the edited versions in Photos, but Photos does not allow us to add further adjustments to the versions edited in Aperture. We have to revert them to the original, before we can modify them in any way.

Yes, Classic is the way to go. LRC has a concept called Smart Collections, which resembles Smart Albums.