Bitcoin is the only focus of the project and its core developers. However, opt in integrations are present for several altcoins:

BGold (BTG) (also known as Bitcoin Gold)
BPlus (XBC) (also known as Bitcoin Plus)
Bitcore (BTX)
Dash (DASH)
Dogecoin (DOGE)
Feathercoin (FTC)
Groestlcoin (GRS)
Htmlcoin (HTML) (also known as Althash)
Liquid Bitcoin (LBTC) (comes with Liquid Tether support USDt) (notes on deployment & usage)

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Litecoin (LTC)
Monacoin (MONA)

Monero (XMR)

(guide on deployment and usage)
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Polis (POLIS)
Viacoin (VIA)