There are other exchange traded products similar to ETFs (such as XTBs) but are specifically built to trade an underlying bond on the exchange, rather than an index.
With an ETF you don’t own any part of the underlying asset. The fund itself is what owns the asset. Similar to a bond fund, you own a share of the fund and buy or sell that share. This exposes the ETF to the same fluctuations as stocks, and removes the legal obligations of bonds.