I don't think there are any clones, as for alternatives, whats your use case and how many do you need?
Mouser have 387 ATMEGA1284RFR2-ZU's in stock if that helps.
https://www.mouser.co.uk/ProductDetail/Microchip-Technology/ATMEGA1284RFR2-ZU?qs=hq%2FeQWvt0cplE0%252B3WWjaTQ%3D%3D
Thanks, I haven't seen this one. It actually does meet my requirements (as mentioned before, 44 pin at least, 10mhz, 64k Rom, 1~2k ram) ideally avr code could run on it.
The reason I ask for clones/alternatives is that although the model you mentioned is available on mouser today it might be gone tomorrow while certain clones (like stm32 clones gd32) are persistently available at low prices.
So that's what I'm looking for. To port one or two atmega644 designs (that just pretend to be basic logic - the most specific requirement is the pin count and the clock).
Sort of, but you'll probably have to go digging for them: http://www.lgtic.com/lgt8fx8p/
Offhand, there seems to be a fair number of boards (e.g. basic breakout / "nano") using them, and I guess some hits on Aliexpress etc. for e.g. lgt8f328p. So I mean, if you want to give it a try...
Last I looked, AVR-DA were modestly in stock, maybe it's worth adapting the project to that. Or XMEGA. Granted, probably all the stocks are different from when I last looked -- the next best lesson would be to be flexible in your options. Granted, there's a fair difference between classic MEGA, X and Dx: it wouldn't exactly be a trivial porting process. Similar in many respects, but NOT compatible.
More applicable, the (MEGA) -4 series is just stripped-down -8 and such, innit? If a 644 will work, a 648 will surely work (with minor porting). I suppose not 328, but maybe some optimizing and compression can be done to conserve space, if it's only marginally over 32k. Between those, and footprint options, you should have a couple dozen parts to choose from, some of which are likely in stock.
Tim
I have heard about lgt8f328p, but the amount of flash isn't sufficient at only 32k. Something like that would be great if it had 64k (128k even better).
Regarding other microchip products, their availability is so hit and miss I would much prefer to avoid them altogether. This is not a commercial project (you could call it a hobby project), but once I port the software to the new chip there is potential for maybe 10 units per month to be required for years(attractively priced) . As it is not commercial I can't buy few hundred at start. I'm looking for something that is likely to be available.
Additionally I think once current stocks run out we're not going back to the previous availability of various microcontrollers.
The only way we're going to see cheap microcontrollers is the way RPi Rp2040 was done. New design made in a modern process.
This is why I mentioned gd32. It is a great example. It is different enough to not be a drop in replacement (ij timing critical stuff at least) so it seems to be continually available cheaper than stm32.