I installed 21.02.0 and ever since there is no Switch menu anymore under Network. I've read elsewhere that the Switch menu is deactivated when there is no physical switch in the device. However, there does appear to be a switch with MediaTek MT7621AT chipset present.
The model number on the back of the device says "ER-X". I used "openwrt-21.02.0-ramips-mt7621-ubnt_edgerouter-x-squashfs-sysupgrade.bin" for the upgrade, however, I did have to use the "Force" option because there was a mismatch regarding the name. I'm not sure which version was installed before, but it did show a Switch menu entry.