Download the latest Bitcoin Cash compatible release candidate of Bitcoin Unlimited (1.5.1.0-rc1, November 23th, 2018) from:

https://www.bitcoinunlimited.info/download

This is a main release candidate of Bitcoin Unlimited compatible with the Bitcoin Cash specifications you could find here:

• https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/uahf-technical-spec.md (Aug 1st '17 Protocol Upgrade)
• https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/nov-13-hardfork-spec.md (Nov 13th '17 Protocol Upgrade)
• https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/may-2018-hardfork.md (May 15th '18 Protocol Upgrade)
• https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/2018-nov-upgrade.md (Nov 15th '18 Protocol Upgrade)

This release candidate is compatible with both Bitcoin Cash and SV changes to the consensus rules. SV features set is disabled by default, the default policy is to activate the set of changes as defined by the bitcoincash.org.

Although this software has passed normal QA tests, it is currently undergoing longevity testing to validate stability. If you are looking for the most stable software, use the last Official Release (i.e. 1.5.0.2).

List of notable changes and fixes to the code base:

• 10x transaction processing performance
• Extended version message: xversion
• adding a checkpoint at height 556767 both for the SV and the BCH chain

Release notes: https://github.com/BitcoinUnlimited/BitcoinUnlimited/blob/dev/doc/release-notes/release-notes-bucash1.5.1.0-rc1.md

Since this is a release candidate and not an official release the Ubuntu PPA repository is not going to be updated.