DO NOT BUY DEVICES WITH 4MB FLASH / 32MB RAM if you intend to flash an up-to-date and secure OpenWrt version onto it! See 4/32 warning for details.
1) 4/32 devices do not have sufficient resources (flash and/or RAM) to provide secure and reliable operation. See OpenWrt on 4/32 devices what you can do now.
2) OpenWrt support for 4/32 devices has ended in 2022. 19.07.10 was the last official build for 4/32 devices.