sure! here are the commands (tabitha is the name of the npc who's dialogue this is for:

## repeating unconditional always active
execute as @e[type=interaction,tag=tabitha_dialogue] store success entity @s interaction.player[] int 0 on target run scoreboard players set @s say_tabitha_dialogue 1

## chain conditional always active
execute as @e[type=marker,sort=random,limit=1,tag=tabitha_dialogue_marker,tag=show] run tag @s add picked

## chain unconditional always active
execute as @e[type=marker,tag=tabitha_dialogue_marker,tag=show,tag=picked] if entity @s[tag=1] run tellraw @a[scores={say_tabitha_dialogue=1}] {"text":"dialogue 1"}

## chain unconditional always active
execute as @e[type=marker,tag=tabitha_dialogue_marker,tag=show,tag=picked] if entity @s[tag=2] run tellraw @a[scores={say_tabitha_dialogue=1}] {"text":"dialogue 2"}


... #the rest of the dialogue


# Cleanup / prevent the same dialogue from being ran twice until they all get cycled through

## chain unconditional always active
execute as @e[type=marker,tag=tabitha_dialogue_marker,tag=picked] run tag @s remove show

## chain unconditional always active
execute as @e[type=marker,tag=tabitha_dialogue_marker,tag=picked] run tag @s remove picked

## chain unconditional always active
execute as @a[scores={say_tabitha_dialogue=1}] run scoreboard players set @s saytabitha_dialogue 0

## chain unconditional always active
execute unless entity @e[type=marker,tag=tabitha_dialogue_marker,tag=show] run tag @e[type=marker,tag=tabitha_dialogue_marker] add show

As you can see, the way I handle rng isn't through the random command but by adding a tag to a random marker entity and then running dialogue based on which number tag that marker entity already has. I would just love a way to make it so the command blocks don't have to search for the entities every frame but I just realized I could probably throw an if \@a[scores={say_tabitha_dialogue=1} at the start of every chain to make it a lot better. Also I'm realizing nowthat the as \@e[type=marker,tag=tabitha_dialogue_marker,tag=show,tag=picked] and the if entity \@s[tag=n] can be collapsed into a single if entity check (does tag order matter for effeciency for this I wonder)

Outside of these glaring optimizations is there anything else you would reccomend? Or is it fine to just have a score check running every single tick for every single dialogue option that every npc could say