The output of rad inbox -h claims there is a --repo option:

15:00:03 [❌ 1 ERROR] > cargo run -q -p radicle-cli -- inbox -h
rad-inbox pre-release
Manage your Radicle notifications

Usage

    rad inbox [<option>...]
    rad inbox list [<option>...]
    rad inbox show <id> [<option>...]
    rad inbox clear [<option>...]

    By default, this command lists all items in your inbox.
    If your working directory is a Radicle repository, it only shows item
    belonging to this repository, unless `--all` is used.

    The `rad inbox show` command takes a notification ID (which can be found in
    the `list` command) and displays the information related to that
    notification. This will mark the notification as read.

    The `rad inbox clear` command will delete all notifications in the inbox.

Options

    --all                Operate on all repositories
    --repo <rid>         Operate on the given repository (default: rad .)
    --sort-by <field>    Sort by `id` or `timestamp` (default: timestamp)
    --reverse, -r        Reverse the list
    --show-unknown       Show any updates that were not recognized
    --help               Print help

When I try it, it fails:

15:00:14 > cargo run -p radicle-cli --  --repo rad:zd4kAF7rQFKbCHAdbcF6zVkx8MyN inbox
    Finished dev [unoptimized + debuginfo] target(s) in 0.11s
     Running `/home/liw/tmp/cargo/debug/rad --repo 'rad:zd4kAF7rQFKbCHAdbcF6zVkx8MyN' inbox`
✗ Error: rad: invalid option '--repo'
15:00:14 > cargo run -p radicle-cli --  --repo rad:zd4kAF7rQFKbCHAdbcF6zVkx8MyN inbox
    Finished dev [unoptimized + debuginfo] target(s) in 0.11s
     Running `/home/liw/tmp/cargo/debug/rad --repo 'rad:zd4kAF7rQFKbCHAdbcF6zVkx8MyN' inbox`
✗ Error: rad: invalid option '--repo'

15:00:28 [❌ 1 ERROR] > cargo run -p radicle-cli -- inbox --repo rad:zd4kAF7rQFKbCHAdbcF6zVkx8MyN 
    Finished dev [unoptimized + debuginfo] target(s) in 0.11s
     Running `/home/liw/tmp/cargo/debug/rad inbox --repo 'rad:zd4kAF7rQFKbCHAdbcF6zVkx8MyN'`
✗ Error: rad inbox: invalid option '--repo'

This is with commit h6030a5d5a467e499d47c0fc4961e330e9ed717e5