The title may be vague (but I did that purposely to not make the question too confusing), but I'll explain more specifics/details here.
First of all, I am looking for a method to not just get rid of phantoms, but effectively cease their spawning. I am aware that repeating command blocks and /gamerule doInsomnia (lets you toggle phantom spawning) exist, but I find repeating command blocks to get slightly laggy sometimes, and they also clog up my logs with messages of "unable to run" (basically spamming the logs with useless outputs), and I am playing on 1.14, meaning I do not have access to the phantom-toggle gamerule (I believe it was added in 1.15 19w36a).
Note that I am playing completely vanilla, and to ensure only working answers I'll mention again that this question is only focusing on Java Edition, not bedrock or console.
To be more specific, I am playing version 1.14.4, if this line is needed.
Either a physical method (such as something like insomnia/bed manipulation or something like that) or actual commands would be fine, but if the only solution is through repeating command blocks that kill phantoms, then I will still take it as an answer.
While I do know that I might be able to make a slow redstone clock that periodically kills phantoms, I would prefer a physical solution.
(Side note: I have marked the question as "minecraft-commands", but if this tag does not fit or if the question is missing tags, then feel free to add them.)