MC-152197@s selector doesn't work in /data commands
You need a sign and an entity to test this commands.
Replace <pos of sign> with the coords of your sign.
/execute as @e[type=!minecraft:player,limit=1,sort=nearest] run data merge block <pos of sign> {Text1:'{"extra":[{"text":"Name: "},{"selector":"@s"}],"text":""}'}
/execute as @e[type=!minecraft:player,limit=1,sort=nearest] run data modify block <pos of sign> Text1 set value '{"extra":[{"text":"Health: "},{"nbt":"Health","entity":"@s"}],"text":""}'
