Bingo! We have a winner. Thanks for your help!
[philo@Spooner ~]$ sudo rm /swapfile
[philo@Spooner ~]$ sudo dd if=/dev/zero of=/swapfile count=8192 bs=1MiB
8192+0 records in
8192+0 records out
8589934592 bytes (8,6 GB, 8,0 GiB) copied, 81,3466 s, 106 MB/s
[philo@Spooner ~]$ sudo chmod 600 /swapfile
[philo@Spooner ~]$ sudo mkswap /swapfile
Setting up swapspace version 1, size = 8 GiB (8589930496 bytes)
no label, UUID=86aa8626-304d-424e-9830-b681d5ac614b
[philo@Spooner ~]$ sudo swapon /swapfile
[philo@Spooner ~]$ free -h
total used free shared buff/cache available
Mem: 7,7Gi 4,7Gi 268Mi 828Mi 2,7Gi 1,9Gi
Swap: 8,0Gi 0B 8,0Gi