I do not consider different front ends as competitors.
If they use the same blockchain, then they are really not competitors.
If they use a different Blockchain, then they are competitors.
They can be both over time.
We saw applications switching blockchains.
For example Musing switched from the Hive blockchain to the Avalanche blockchain.
It was not a competitor of the Hive blockchain in the past, but nowadays it is.
DTube also switched from the Hive blockchain to the Avalon blockchain, but you can still post from there to the Steem and the to the Hive blockchain, so it is somewhat interoperable.
DLive first used the Steem blockchain, then the Lino blockchain, then (following its acquisition by BitTorrent in 2019) the Tron blockchain.
And of course our most known example is Steem Monsters/Splinterlands, which switched from the Steem blockchain to the Hive blockchain.