In snapshot 21w20a, was added an option to make entities to have visual fire trought a command, it works even in boats, but it doesn't work on blazes.

How to reproduce:

1.- Write the next command on chat (Make sure to have cheats on, or OP permissions):

/summon minecraft:creeper ~ ~ ~

This will summon a creeper with visual fire in your position.

2.- Write the next command on chat (Make sure to have cheats on, or OP permissions):

/summon minecraft:boat ~ ~ ~

This will summon a boat with visual fire in your position

3.- Write the next command on chat (Make sure to have cheats on, or OP permissions):

/summon minecraft:blaze ~ ~ ~

This will summon a blaze in your position, but this blaze will no have visual fire unless you are on survival, but that is a common thing.

Note: The photo is from a video that i made.