The bossbar text covers narrator text if it stacks up to the top of the screen. The text is tinted like everything behind narrator text but still renders before it, Relates to MC-193511.

To replicate:

1. Go to Game Menu>Options>Accesibility Settings and turn on Narrator if it isn't already
2. Recommended (not required) turn off speaker
3. In Game Menu>Options>Music&Sounds... ensure Ambient/Environment is on (used in commands)
4. In order to consistently get enough sounds put the following commands in repeating command blocks that are on:
   /playsound minecraft:entity.slime.death ambient @p
   /playsound minecraft:entity.stray.death ambient @p
   /playsound minecraft:entity.skeleton.death ambient @p
   /playsound minecraft:entity.chicken.death ambient @p
   /playsound minecraft:entity.parrot.death ambient @p
   /playsound minecraft:entity.pig.death ambient @p
   /playsound minecraft:entity.sheep.death ambient @p
   /playsound minecraft:entity.cow.death ambient @p
   /playsound minecraft:entity.turtle.death ambient @p
   /playsound minecraft:entity.fox.death ambient @p
   /playsound minecraft:entity.polar_bear.death ambient @p
   /playsound minecraft:entity.panda.death ambient @p
   /playsound minecraft:entity.wolf.death ambient @p
   /playsound minecraft:entity.cat.death ambient @p
   /playsound minecraft:entity.ocelot.death ambient @p
   /playsound minecraft:entity.bee.death ambient @p
   /playsound minecraft:entity.magma_cube.death ambient @p
   /playsound minecraft:entity.ender_dragon.death ambient @p
   /playsound minecraft:entity.enderman.death ambient @p
   /playsound minecraft:entity.creeper.death ambient @p
   /playsound minecraft:entity.spider.death ambient @p
   /playsound minecraft:entity.zombified_piglin.death ambient @p
   /playsound minecraft:entity.husk.death ambient @p
   /playsound minecraft:entity.zombie.death ambient @p
5. Make sure screen is full
6. Run these commands and observe the rendering issues:

Create Bossbar (Command Block)

/bossbar add longbossbar ["",\{"text":"ABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZ","bold":true,"underlined":true,"strikethrough":true}]

Display Bossbar

/bossbar set minecraft:longbossbar players @p

Add numbers after longbossbar for up to 4 bossbars (longbossbar2,longbossbar3,longbossbar4)