OK, I’m such an idiot, I never thought that they would still make these things in big leaded packages.

See https://uk.rs-online.com/web/p/microcontrollers/1331672/

For an Attiny 85 in 8 pin DIP for £1.

And you can bet that it is genuine, from RS.

Get some plug-in breadboard, a USBasp, ribbon cable, headers, a few passives, then develop-away.

I’ll probably pick up a dozen, next time I am home, from the local depot.