Mempool[1] and BTC RPC Explorer[2] are 2 option frequently mentioned here, where mempool have lots of feature and configuring BTC RPC explorer isn't hard. If you're strictly want C# based explorer, the most popular option is Blockcore explorer[3]. Although i never see anyone use or talk about it.
[1] https://github.com/mempool/mempool
[2] https://github.com/janoside/btc-rpc-explorer/
[3] https://github.com/block-core/blockcore-explorer
I use BTC-RPC-Explorer on another older notebook along with electrcs and it has served me well, I haven't tested the mempool yet.
The guides I used for installations are this one: https://raspibolt.org/guide/bitcoin/electrum-server.html , https://raspibolt.org/guide/bitcoin/blockchain-explorer.html