UngeheuerLich
Legend
I would allow that, as it at least follows some kind of logic.Under Improvised Weapons:
Often, an improvised weapon is similar to an actual weapon and can be treated as such. For example, a table leg is akin to a club. At the DM's option, a character proficient with a weapon can use a similar object as if it were that weapon and use his or her proficiency bonus.Because the fiery blade is similar to a scimitar, it can be treated as a scimitar which does 1d6 damage.
But it uses dex to attack then and does 1d6+dex damage instead of 3d6. Then you can use extra attack and also use an off hand attack with another light weapon.
I still would prefer the 2024 rules just remove such dumb wordings, where you "use an action to make an attack".