Basically what the title says. If you first place a redstone block down and then a command block next to it (doesn't matter which type), change it to repeating and enter a command (such as: say hi!) it doesn't give output unless updated, either before or after the command was entered.

Feels related to MC-86846 and possibly MC-149038, not sure about that one.

Also was able to reproduce in 12.2, 13.2, 14.4, but this behaviour may then also have been produced by MC-86846 in the case where the command block was powered and on 'needs redstone' mode.

Easily read reproduction steps:

• place down redstone block
• place command block next to it
• set mode to repeating and enter any command (e.g. say hi)
• no output
• update command block (placing block next to it, breaking a block, (soft) powering it with redstone (again), etc.)
• output starts